A Linguist’s Tree of Knowledge: An Introduction to the Tree Diagram

The tree diagram is a newer method for diagramming sentences that is most commonly used by linguists and other academic professionals. While the Reed Kellogg diagram was considered an effective tool for students to visualize sentence structure, it had many limitations. It dispensed with traditional word order and used a variety of occasionally confusing symbols, meaning the resulting diagram was difficult to understand for anyone unfamiliar with the method.

Reed and Kellogg did introduce two core grammatical concepts: Constituency, how a word relates to the larger structure of a sentence, and dependency, how a word is dependent upon each one that precedes it. The primary goal of a tree diagram is to illustrate these concepts in a way that is visibly apparent, even for those previously unfamiliar with sentence diagrams.

In a tree diagram, a sentence is divided into two parts: a subject and a predicate. They are made up of noun phrases or verb phrases. These are groups of words that include a noun or verb and any words that add as modifiers. The subject is a noun phrase while a predicate is usually a verb phrase. The noun phrase A big dog is comprised of the indefinite article ‘a’, the adjective ‘big’, and the noun ‘dog’. The verb phrase jumped over the fence consists of the verb ‘jumped’ and the prepositional phrase ‘over the fence’.

Unlike a Reed-Kellogg diagram, these components are not separated by slashes and other symbols. Instead, they descend from the subject and predicate in the form of lines acting as branches. This continues until each noun or verb phrase is broken down into its simplest parts. In the end, a sentence diagrammed in this style should look like a vast tree, with the subject and predicate acting as the trunk and the sentence modifiers standing in as the colorful and complex leaves that give it personality.

Now that you understand the basic premise of a Tree Diagram and how it breaks down a sentence, let’s take a look at an example.

Seen here, the sentence is broken down into a subject and predicate. The subject is a noun phrase that consists of the indeterminate article ‘the’ and the noun ‘dog’. The predicate is more complex, as it consists of both a verb and a noun phrase. Breaking down the predicate, the verb is ‘ate’ and the noun phrase is ‘the’ (indefinite article) and ‘bone’ (noun). As you can see, the tree diagram uses minimal symbols and little complex jargon, yet clearly illustrates how each of these words relate to and depend upon each other.

Here is another example of a tree diagram. As you can see, this one is a bit more intricate. Let’s take a look and break it down.

Once again, the sentence is divided into a subject and predicate. The subject is composed of a noun phrase: ‘the’ as an indefinite article and ‘teacher’ as a noun. The predicate is more complex than before. Its verb phrase consists of three parts: the verb ‘gave’; the noun ‘homework’; and the prepositional phrase ‘to his students’. Are you starting to get a better understanding of constituency and dependency now?

Unfortunately, tree diagrams do have some negative aspects. Like the Reed-Kellogg diagram, more complex tree diagrams can take up a great deal of space and become more difficult to decipher in the process. Additionally, as both a strength and weakness, they are more open to interpretation than the Reed-Kellogg diagram. It is possible for a sentence to have multiple, different, and equally valid tree diagrams depending upon which unit is focused on, especially with a sentence taken from classic literature.

As a whole, tree diagrams offer a clear and more nuanced look at sentence structure without sacrificing traditional word order. While they are primarily used by grammarians and other linguistic specialists, they are quickly becoming the standard method of sentence diagramming, as the result is easily comprehensible to everyone. If you are seeking to improve your writing, I recommend that you try diagramming at least one sentence a day using this method. In doing so, you will gain a greater understanding of how to compose grammatically correct, diverse, and impactful sentences.

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